In the early 1990s, Dow Chemical Co. disclosed [Me2Si(Me4C5)NtBu]TiCl2 (Constrained-Geometry Catalyst, hereinafter simply referred to as CGC) (U.S. Pat. No. 5,064,802). CGC shows excellent properties in a copolymerization reaction of ethylene and α-olefin, as compared to conventional metallocene catalysts. Its main two excellent properties can be summarized as follows: (1) CGC can be used to form high molecular weight polymers due to its high activity at high polymerization temperature, and (2) CGC can be used for copolymerization of α-olefin having large steric hindrance, such as 1-hexene and 1-octene. As many useful properties of CGC are disclosed, in addition to these properties described above, research into synthesis of CGC derivatives as a polymerization catalyst is increasingly conducted in academic and industrial fields.
As one example of such approaches, synthesis of metal compounds comprising other various bridges instead of a silicon bridge and containing a nitrogen substituent, and polymerization using these metal compounds were performed. Examples of such metal compounds include Compounds (1) through (4) (Chem. Rev. 2003, 103, 283).

Compounds (1) through (4) respectively contain a phosphorus bridge (1), an ethylene or propylene bridge (2), a methylidene bridge (3), and a methylene bridge (4), instead of the silicon bridge of the CGC structure. However, these compounds could not show enhanced activity, copolymerization performance, or the like when ethylene is polymerized or when ethylene and α-olefin are copolymerized, as compared to CGC.
In another example of the approaches, a great number of compounds, in which an amino ligand in CGC is replaced with an oxido ligand, have been synthesized. There have been attempts to use such compounds for polymerization. Examples of such compounds include those represented by Formulae below:

In Compound (5), which was developed by T. J. Marks, et al., a cyclopentadiene (Cp) derivative is bridged to an oxido ligand by an ortho-phenylene group (Organometallics 1997, 16, 5958). A compound having the same bridge and polymerization using the complex were reported by Mu et al. (Organometallics 2004, 23, 540). A compound in which an indenyl ligand is bridged to an oxido ligand by an ortho-phenylene group was reported by Rothwell, et al. (Chem. Commun. 2003, 1034). In Compound (6), which was reported by Whitby, et al., a cyclopentadienyl ligand is bridged to an oxido ligand by three carbon atoms (Organometallics 1999, 18, 348). As reported, Compound (6) shows activity in syndiotactic polystylene polymerization. Similar compounds were also reported by Hessen, et al. (Organometallics 1998, 17, 1652). Compound (7), which was reported by Rau, et al., showed activity when it is used for ethylene polymerization and ethylene/1-hexene copolymerization at a high temperature and a high pressure (210° C., 150 Mpa) (J. Organomet. Chem. 2000, 608, 71). Synthesis of Compound (8), which has a similar structure to the compound, and a high-temperature and high-pressure polymerization using the compound was filed in patent application by Sumitomo Co. (U.S. Pat. No. 6,548,686).
However, only some of these catalysts as described above are used in commercial plants. Accordingly, there is a need to develop a catalyst exhibiting enhanced polymerization performance, and a method for simply preparing the catalyst.